1. Field of the Invention
The present invention relates generally to devices for presenting three-dimensional images to viewers. More particularly, the invention relates to a device having fixed or movable louvers capable of isolating right and left stereoscopic images for one or more viewers located within a generally fixed area spaced-away from the viewing device.
Three-dimensional or stereoscopic viewing relies on the presentation to the viewer of a pair of images of the same scene or object, where the images differ only in parallax corresponding to the distance between the viewer's eyes. Usually, the images are taken by a stereoscopic camera having a pair of lenses spaced-apart by a distance approximately equal to that between a pair of eyes. A number of devices have been developed for viewing such pairs of images in order to enhance the apparent three-dimensionality.
Perhaps the best known of such devices are hand-held stereoscopic viewers (stereoscopes), such as the Viewmaster.RTM., where right and left images are totally isolated by a barrier, lens viewing mechanism, or both. Such devices, of course, are only suitable for one viewer at a time and are generally limited to viewing still images.
For groups of viewers, systems have been developed for isolating right and left images which are simultaneously projected onto a screen. Usually, the images are distinguishable, for example by color or polarization, and the viewer wears glasses having lenses capable of transmitting only one image to each eye. For example, images projected simultaneously in red and green may be filtered from each other using green and red filters. Alternatively, images polarized by 90.degree. may be simultaneously projected and separated by correspondingly oriented polarized lenses. While such three-dimensional viewing systems are generally functional, many viewers object to having to wear glasses. However, the use of colored images for isolation generally limits the ability to project full color images, and the isolation provided by polarization of images is not complete.
It has long been an object to be able to present three-dimensional images to groups and audiences without the need for the individual viewers to wear glasses or other apparatus for isolating images. A number of systems have been proposed to such end. For example, simultaneously projected polarized images may be isolated by placing a pair of large polarizing screens between the audience and the images. The screens may then be shifted laterally in order to isolate the images from the right and left eyes, respectively. Although functional in theory, as a practical matter the polarizing screens are not sufficiently effective in isolating images to present a quality three-dimensional image.
For the above reasons, it would be desirable to provide improved systems for presenting three-dimensional images to groups of viewers, where the viewers do not need to wear image isolating devices, such as filter glasses.
2. Description of the Background Art
Stereoscopic imaging devices are described in U.S. Pat. Nos. 2,639,653; 2,974,562; 3,334,179; 3,439,972; 3,495,891; and 4,469,415; and in Japanese patent No. 60-37520. U.S. Pat. No. 2,974,562 describes a viewer which isolates polarized right and left images using a pair of transparent polarizing panels. By shifting the panels back and forth, view of a common screen can be alternately blocked for the left and right eyes. A similar concept is disclosed in U.S. Pat. No. 3,439,972, where two images are divided into a plurality of parallel vertical strips, and a vertical grating is used to isolate alternate strips from the right and left eyes respectively.